The java.sql.Timestamp class has no format. Its toString method generates a String with a format.
Do not conflate a date-time object with a String that may represent its value. A date-time object can parse strings and generate strings but is not itself a string.
First convert from the troubled old legacy date-time classes to java.time classes. Use the new methods added to the old classes.
Instant instant = mySqlDate.toInstant() ;
Lose the fraction of a second you don't want.
instant = instant.truncatedTo( ChronoUnit.Seconds );
Assign the time zone to adjust from UTC used by Instant.
ZoneId z = ZoneId.of( "America/Montreal" ) ;
ZonedDateTime zdt = instant.atZone( z );
Generate a String close to your desired output. Replace its T in the middle with a SPACE.
DateTimeFormatter f = DateTimeFormatter.ISO_LOCAL_DATE_TIME ;
String output = zdt.format( f ).replace( "T" , " " );